/*
 * jdcolor.c
 *
 * Copyright (C) 1991-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains output colorspace conversion routines.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private subobject */

typedef struct
{
	struct jpeg_color_deconverter pub;	/* public fields */

	/* Private state for YCC->RGB conversion */
	int            *Cr_r_tab;	/* => table for Cr to R conversion */
	int            *Cb_b_tab;	/* => table for Cb to B conversion */
	INT32          *Cr_g_tab;	/* => table for Cr to G conversion */
	INT32          *Cb_g_tab;	/* => table for Cb to G conversion */
} my_color_deconverter;

typedef my_color_deconverter *my_cconvert_ptr;


/**************** YCbCr -> RGB conversion: most common case **************/

/*
 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
 * The conversion equations to be implemented are therefore
 *	R = Y                + 1.40200 * Cr
 *	G = Y - 0.34414 * Cb - 0.71414 * Cr
 *	B = Y + 1.77200 * Cb
 * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
 *
 * To avoid floating-point arithmetic, we represent the fractional constants
 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
 * the products by 2^16, with appropriate rounding, to get the correct answer.
 * Notice that Y, being an integral input, does not contribute any fraction
 * so it need not participate in the rounding.
 *
 * For even more speed, we avoid doing any multiplications in the inner loop
 * by precalculating the constants times Cb and Cr for all possible values.
 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
 * for 12-bit samples it is still acceptable.  It's not very reasonable for
 * 16-bit samples, but if you want lossless storage you shouldn't be changing
 * colorspace anyway.
 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
 * values for the G calculation are left scaled up, since we must add them
 * together before rounding.
 */

#define SCALEBITS	16			/* speediest right-shift on some machines */
#define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
#define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))


/*
 * Initialize tables for YCC->RGB colorspace conversion.
 */

LOCAL void build_ycc_rgb_table(j_decompress_ptr cinfo)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	int             i;
	INT32           x;
	SHIFT_TEMPS
		cconvert->Cr_r_tab = (int *)
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE + 1) * SIZEOF(int));
	cconvert->Cb_b_tab = (int *)(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE + 1) * SIZEOF(int));

	cconvert->Cr_g_tab = (INT32 *)
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE + 1) * SIZEOF(INT32));
	cconvert->Cb_g_tab = (INT32 *)
		(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE + 1) * SIZEOF(INT32));

	for(i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++)
	{
		/* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
		/* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
		/* Cr=>R value is nearest int to 1.40200 * x */
		cconvert->Cr_r_tab[i] = (int)RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
		/* Cb=>B value is nearest int to 1.77200 * x */
		cconvert->Cb_b_tab[i] = (int)RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
		/* Cr=>G value is scaled-up -0.71414 * x */
		cconvert->Cr_g_tab[i] = (-FIX(0.71414)) * x;
		/* Cb=>G value is scaled-up -0.34414 * x */
		/* We also add in ONE_HALF so that need not do it in inner loop */
		cconvert->Cb_g_tab[i] = (-FIX(0.34414)) * x + ONE_HALF;
	}
}


/*
 * Convert some rows of samples to the output colorspace.
 *
 * Note that we change from noninterleaved, one-plane-per-component format
 * to interleaved-pixel format.  The output buffer is therefore three times
 * as wide as the input buffer.
 * A starting row offset is provided only for the input buffer.  The caller
 * can easily adjust the passed output_buf value to accommodate any row
 * offset required on that side.
 */

METHODDEF void
ycc_rgb_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	register int    y, cb, cr;
	register JSAMPROW outptr;
	register JSAMPROW inptr0, inptr1, inptr2;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->output_width;

	/* copy these pointers into registers if possible */
	register JSAMPLE *range_limit = cinfo->sample_range_limit;
	register int   *Crrtab = cconvert->Cr_r_tab;
	register int   *Cbbtab = cconvert->Cb_b_tab;
	register INT32 *Crgtab = cconvert->Cr_g_tab;
	register INT32 *Cbgtab = cconvert->Cb_g_tab;

	SHIFT_TEMPS while(--num_rows >= 0)
	{
		inptr0 = input_buf[0][input_row];
		inptr1 = input_buf[1][input_row];
		inptr2 = input_buf[2][input_row];
		input_row++;
		outptr = *output_buf++;
		for(col = 0; col < num_cols; col++)
		{
			y = GETJSAMPLE(inptr0[col]);
			cb = GETJSAMPLE(inptr1[col]);
			cr = GETJSAMPLE(inptr2[col]);
			/* Range-limiting is essential due to noise introduced by DCT losses. */
			outptr[RGB_RED] = range_limit[y + Crrtab[cr]];
			outptr[RGB_GREEN] = range_limit[y + ((int)RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS))];
			outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]];
			outptr += RGB_PIXELSIZE;
		}
	}
}


/**************** Cases other than YCbCr -> RGB **************/


/*
 * Color conversion for no colorspace change: just copy the data,
 * converting from separate-planes to interleaved representation.
 */

METHODDEF void
null_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
{
	register JSAMPROW inptr, outptr;
	register JDIMENSION count;
	register int    num_components = cinfo->num_components;
	JDIMENSION      num_cols = cinfo->output_width;
	int             ci;

	while(--num_rows >= 0)
	{
		for(ci = 0; ci < num_components; ci++)
		{
			inptr = input_buf[ci][input_row];
			outptr = output_buf[0] + ci;
			for(count = num_cols; count > 0; count--)
			{
				*outptr = *inptr++;	/* needn't bother with GETJSAMPLE() here */
				outptr += num_components;
			}
		}
		input_row++;
		output_buf++;
	}
}


/*
 * Color conversion for grayscale: just copy the data.
 * This also works for YCbCr -> grayscale conversion, in which
 * we just copy the Y (luminance) component and ignore chrominance.
 */

METHODDEF void
grayscale_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
{
	jcopy_sample_rows(input_buf[0], (int)input_row, output_buf, 0, num_rows, cinfo->output_width);
}


/*
 * Adobe-style YCCK->CMYK conversion.
 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
 * conversion as above, while passing K (black) unchanged.
 * We assume build_ycc_rgb_table has been called.
 */

METHODDEF void
ycck_cmyk_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
{
	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	register int    y, cb, cr;
	register JSAMPROW outptr;
	register JSAMPROW inptr0, inptr1, inptr2, inptr3;
	register JDIMENSION col;
	JDIMENSION      num_cols = cinfo->output_width;

	/* copy these pointers into registers if possible */
	register JSAMPLE *range_limit = cinfo->sample_range_limit;
	register int   *Crrtab = cconvert->Cr_r_tab;
	register int   *Cbbtab = cconvert->Cb_b_tab;
	register INT32 *Crgtab = cconvert->Cr_g_tab;
	register INT32 *Cbgtab = cconvert->Cb_g_tab;

	SHIFT_TEMPS while(--num_rows >= 0)
	{
		inptr0 = input_buf[0][input_row];
		inptr1 = input_buf[1][input_row];
		inptr2 = input_buf[2][input_row];
		inptr3 = input_buf[3][input_row];
		input_row++;
		outptr = *output_buf++;
		for(col = 0; col < num_cols; col++)
		{
			y = GETJSAMPLE(inptr0[col]);
			cb = GETJSAMPLE(inptr1[col]);
			cr = GETJSAMPLE(inptr2[col]);
			/* Range-limiting is essential due to noise introduced by DCT losses. */
			outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])];	/* red */
			outptr[1] = range_limit[MAXJSAMPLE - (y +	/* green */
												  ((int)RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS)))];
			outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])];	/* blue */
			/* K passes through unchanged */
			outptr[3] = inptr3[col];	/* don't need GETJSAMPLE here */
			outptr += 4;
		}
	}
}


/*
 * Empty method for start_pass.
 */

METHODDEF void start_pass_dcolor(j_decompress_ptr cinfo)
{
	/* no work needed */
}


/*
 * Module initialization routine for output colorspace conversion.
 */

GLOBAL void jinit_color_deconverter(j_decompress_ptr cinfo)
{
	my_cconvert_ptr cconvert;
	int             ci;

	cconvert = (my_cconvert_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_color_deconverter));
	cinfo->cconvert = (struct jpeg_color_deconverter *)cconvert;
	cconvert->pub.start_pass = start_pass_dcolor;

	/* Make sure num_components agrees with jpeg_color_space */
	switch (cinfo->jpeg_color_space)
	{
		case JCS_GRAYSCALE:
			if(cinfo->num_components != 1)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			break;

		case JCS_RGB:
		case JCS_YCbCr:
			if(cinfo->num_components != 3)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			break;

		case JCS_CMYK:
		case JCS_YCCK:
			if(cinfo->num_components != 4)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			break;

		default:				/* JCS_UNKNOWN can be anything */
			if(cinfo->num_components < 1)
				ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
			break;
	}

	/* Set out_color_components and conversion method based on requested space.
	 * Also clear the component_needed flags for any unused components,
	 * so that earlier pipeline stages can avoid useless computation.
	 */

	switch (cinfo->out_color_space)
	{
		case JCS_GRAYSCALE:
			cinfo->out_color_components = 1;
			if(cinfo->jpeg_color_space == JCS_GRAYSCALE || cinfo->jpeg_color_space == JCS_YCbCr)
			{
				cconvert->pub.color_convert = grayscale_convert;
				/* For color->grayscale conversion, only the Y (0) component is needed */
				for(ci = 1; ci < cinfo->num_components; ci++)
					cinfo->comp_info[ci].component_needed = FALSE;
			}
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_RGB:
			cinfo->out_color_components = RGB_PIXELSIZE;
			if(cinfo->jpeg_color_space == JCS_YCbCr)
			{
				cconvert->pub.color_convert = ycc_rgb_convert;
				build_ycc_rgb_table(cinfo);
			}
			else if(cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
			{
				cconvert->pub.color_convert = null_convert;
			}
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		case JCS_CMYK:
			cinfo->out_color_components = 4;
			if(cinfo->jpeg_color_space == JCS_YCCK)
			{
				cconvert->pub.color_convert = ycck_cmyk_convert;
				build_ycc_rgb_table(cinfo);
			}
			else if(cinfo->jpeg_color_space == JCS_CMYK)
			{
				cconvert->pub.color_convert = null_convert;
			}
			else
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;

		default:
			/* Permit null conversion to same output space */
			if(cinfo->out_color_space == cinfo->jpeg_color_space)
			{
				cinfo->out_color_components = cinfo->num_components;
				cconvert->pub.color_convert = null_convert;
			}
			else				/* unsupported non-null conversion */
				ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
			break;
	}

	if(cinfo->quantize_colors)
		cinfo->output_components = 1;	/* single colormapped output component */
	else
		cinfo->output_components = cinfo->out_color_components;
}
